After the venous injection of radioisotope, images are
collected over three minute intervals. DTPA is one of four
types of radionuclide agents used in imaging of the kidney.
It is filtered through the glomerulus so it is useful in
detecting perfusion of the kidney and glomerular
filtration. It does not demonstrate function of the
renal tubules.

The images are read from left to right and from top to
bottom. Note that, unlike x-rays, nuclear renograms show
the left kidney on the left side (as you face the scan).
The data collected by the camera is analyzed by a computer
and plotted on a time graph. Counts (how much isotope is in
the kidneys) is shown on the Y axis and time from injection
is shown on the X axis. The response of each kidney is
plotted separately.

Notice that both kidneys take up the isotope rapidly (the
curves are steeply rising between 1 and 3 minutes). The
concentration of the isotope peaks at 4-6 minutes and then
starts to fall. Normally at least half of the isotope is
excreted and drained from the kidneys within 20 minutes.
When obstruction is suspected, a diuretic is given 15
minutes after injection of the isotope to increase urine
production. This will wash the isotope out of an enlarged
kidney pelvis as long as there is no obstruction to urine
flow into the bladder. See a scan
showing obstruction.